Wicked star Mamie Parris, above, has an understudy who defied grave expectations as Elphaba in "Wicked" has a understudy.

Seasoned theatergoers will likely recognize the sinking feeling David Vest experienced at the Sunday afternoon performance of “Wicked.”

The national tour of the blockbuster musical — starring Mamie Parris as Elphaba and Alli Mauzey as Glinda — is having a fourth, robust production at Denver’s Buell Theatre.

“I was disappointed when I first saw the insert that Mamie Parrish would not be in this show,” wrote Vest in a morning email. “I immediately went to the who’s who,” he continued, where he was again let down to see that the understudy didn’t have “any real credits.”